SOLID LIQUID LUBRICATION OF CERAMICS AT ELEVATED-TEMPERATURES/

This study investigates the effects of solid and liquid lubrication on the friction and wear performance of silicon nitride (Si3N4) and gray cast iron. The solid lubricant was a thin silver film (similar to 2 m u m thick) produced on Si3N4 by ion-beam-assisted deposition. A high-t emperature polyol-ester-base synthetic oil served as the liquid lubric ant. Friction and wear tests were performed with pin-on-disk and oscil lating-slider wear test machines at temperatures up to 300 degrees C. Without the silver films, the friction coefficients of Si3N4/Si3N4 tes t pairs were 0.05-0.14, and the average wear rates of Si3N4 pins were similar to 5 x 10(-8) mm(3) N-1 m(-1). The friction coefficients of Si 3N4/cast iron test pairs ranged from 0.08 to 0.11, depending on test t emperature. The average specific wear rates of cast iron pins were sim ilar to 3 X 10(-7) mm(3) N-1 m(-1). However, simultaneous use of the s olid-lubricant silver and synthetic oil on the sliding surfaces reduce d friction coefficients to 0.02-0.08. Moreover, the wear of Si,N, pins and silver-coated Si,N, disks was so low that it was difficult to ass ess by a surface profilometer. The wear rates of cast iron pins were s imilar to 7 x 10(-9) mm(3) N-1 m(-1) up to 250 degrees C, but showed a tendency to increase slightly at higher temperatures. In general, the test results demonstrated that the solid/liquid lubrication of cerami c and/or metallic components is both feasible and effective in control ling friction and wear. (C) 1997 Elsevier Science S.A.